In the past few years there have been a number of programs in this country and abroad to develop very small remotely controlled aircraft for both military and civilian use. These craft have been dubbed Mini-Remotely Piloted Vehicles (Mini-RPV's). The low speed (less than 150 knots) and small power requirement (less than 25 hp) for Mini-RPVs dictate that the best propulsion system for such vehicles is a propeller driven by a reciprocating engine.
In many of the Mini-RPV programs attention was focused on the electronics of navigation, guidance and control systems and/or certain special electronic sensors. This attention was necessary because much of the electronics involved new technology. However, it was found that insufficient attention had been paid to the more mundane power plant problem. The several go kart and industrial engines that had been applied to the job were inadequate even with considerable modifications. Reliability, vibration and configuration difficulties had not been surmounted.
The Mini-RPV propulsion problem was recognized over three years ago and in February 1977 the U.S. Army awarded two parallel contracts to develop 20 hp Mini-RPV engines. The present low vibration twin crankshaft engine is the result of work done under one of the above contracts.
Engines of the broad type to which this invention relates are known in the prior art and to comply with the duty of disclosure required by 37 C.F.R. 1.56, the following references are made of record herein: U.S. Pat. Nos. 2,253,490, Bakewell, and 3,332,404, Lovercheck; and July, 1969 issued of Radio Control Modeler, page 35, etc.